Large-diameter pipe is typically made by crimping, that is bending up, the longitudinal edges of a rolled plate, termed a “skelp,” which in the case of pipe of very large diameter may be formed by two or more strips whose longitudinal edges are welded together. This gives the workpiece a cross sectional shape having a flat and planar center portion with a pair of normally upwardly bent edges of part-cylindrical shape having a radius of curvature corresponding to that of the pipe to be produced. This crimped workpiece is then fed to a press that bends it into a U-section, then to a press that bends it into an O-section of basically circular shape with the longitudinal edges abutting or closely juxtaposed. In a final stage the two longitudinal edges are butt-welded together to form a the finished circular-section pipe.
The crimping of the longitudinal plate edges in the first shaping step represents an important step in the process of pipe production, and thus optimizing this step optimizes the production of pipe. In a crimping press, an upper die and a lower die is are provided for each of the two longitudinal plate edges, with the upper die having a downwardly directed convex face and the lower die having a complementary upwardly directed concave face, or vice versa.
To be able to adapt a press to the varying width of the plates, it is known to position each of the two plate edges in an independent press that is designed as a C-frame press. All C-frame presses are generally moved transversely, that is crosswise to the longitudinal direction of the plate workpiece and its edges, and are shifted transversely for adjustment, as described in U.S. Pat. No. 3,911,709 and GB 1,537,055. With the currently known systems, there is room for improvement with respect to stability, for example.